JPS6030477B2 - synchronous signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for generating a synchronization signal that can horizontally shift an image of an arbitrary horizontal scanning line of a television image formed based on the synchronization signal. The present invention relates to a synchronization signal generator, and is particularly suitable for obtaining a synchronization signal for reproducing the influence on television images caused by various defects in a rotating magnetic head device of a VTR.

Generally speaking, the rotary magnetic head device of a broadcasting VTR is
It requires particularly high precision compared to TR.

For example, in a two-head rotary magnetic head device, two magnetic heads must be mounted on the center line of the head disk at an interval of exactly 1800 degrees. In this case, if the two magnetic heads attached to the head disk are misaligned, the positions of the horizontal synchronization signals of the signals reproduced by these magnetic heads will be different from the A field and the B field.
It deviates from the field. As a result, the image moves left and right for each field, resulting in an unstable screen. Therefore, if the A field and B field can be interlaced,
A step is generated between adjacent horizontal scanning lines. Similarly, for a four-head type rotary magnetic head, four magnetic heads must be installed at exactly 900 intervals. In this case, if there is a positional shift in each head, there is a possibility that a step difference will occur in the image within one field of the screen. As described above, the rotary magnetic head device of a VTR must be configured with extremely high precision, but conventionally it has been difficult to quantitatively recognize whether the above-mentioned head positional deviation has an effect on the image. I couldn't do it.

The present invention has been made in view of the above-mentioned problems, and includes:
When multiple heads of a rotating head device of a video signal recording and reproducing device such as a VTR are not mounted on the head mounting body at equal intervals and are misaligned with each other, or when a VTR
, a recording/reproducing device such as a video signal recording/reproducing device such as a VSR in which the axes of the head mounting body of the head device and the recording medium support such as a tape guide cylinder, turntable, etc. are misaligned with respect to each other. This makes it possible to quantitatively recognize the effects on images caused by defects.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a synchronizing signal generator for VTR test signals.

Note that FIG. 2 is a waveform diagram showing the waveforms of each part in FIG. 1, and FIGS. 3A and 3B are explanatory diagrams showing horizontal scanning lines formed on a television screen. In the clock pulse generator 1 shown in FIG. 1, for example, a clock pulse for day 2 of 14.3 is generated.

This clock pulse has a color subcarrier frequency (3.5 MHz).
The frequency is four times that of 2). This clock pulse is the clock pulse of horizontal counter 2. It is supplied to the terminal CP. In this horizontal counter 2, the clock pulse is 1/910
The frequency is divided into Therefore, from the output terminal ○, of the horizontal counter 2, a horizontal synchronizing signal h (Fig. 2 h) with a horizontal frequency of 15.7 KHz is obtained, and from the output terminal 02, a horizontal synchronizing signal h (Fig. signal water is obtained. The signal 2h is supplied to a vertical counter 10, and its frequency is divided into 1/525.

Therefore, from the output terminal ○ of vertical counter 0, it is 59.94.
A vertical synchronization signal v with a vertical frequency (nav) of HZ is obtained. A vertical synchronizing signal V separated from the external video signal is supplied to the reset terminal R of the vertical counter 0 in order to synchronize the counting operation of the vertical counter 10 with the external video signal. The horizontal synchronizing signal h and the vertical synchronizing signal v formed by the horizontal counter 2 and the vertical counter, as well as the binary count outputs of each counter 2 and 10, are supplied to a synchronizing signal forming circuit 3, where they are input at a predetermined timing. and horizontal drive signal HD and vertical drive signal V in the pulse.
Various synchronization signals such as D, synchronization pulse e, and planking pulse BL are formed. A predetermined plurality of binary count outputs of the horizontal counter 2 are output to NAND gates 4, 5, and 5, respectively.
V is supplied to 6.

Then, from the respective output terminals of the NAND gates 4, 5, and 6, the count output a of the horizontal counter 2 for the 91st boat Hayabusa, the counting output a2 of the 91st boat Hayabusa 10k (for example, 916 boats), and the counting output a2 of the 91st boat Hayabusa - 915 boats -
k (for example, 90 Turtle Hayabusa) count outputs a3 are obtained, respectively.
These count outputs, , a2, a3 are line selector 7.
Here one of these outputs is selected and fed back to the reset terminal R of the horizontal counter 2.
The line selector 7 includes a switch 8 as shown in FIG.
, 9, each movable contact is connected to a control terminal S. , 9 of the line selector 7. , S2.

This control terminal S2 is connected to the output terminal ○ of the vertical counter 10.
The vertical synchronization signal v obtained from the flip-flop 11
v/2 pulse whose frequency is divided into 1/2 through (Fig. 2 v/2
) is supplied. Therefore, when this v/2 pulse is at a high level, the movable contact of the switch 8 is connected to the contact 8a, and the 916 count output a2 of the output of the NAND gate 5 is supplied to the contact 9b of the switch 9. Further, when the v/2 pulse is at a low level, the movable contact of the switch 8 is connected to the contact 8b, and the 904 count output a3 of the output of the NAND gate 6 is supplied to the contact 9b of the switch 9. In this way, the count outputs a2 and a3 of 916 Hayabusa and 90 Heart Hayabusa are alternately supplied to the switch 9 for each IV. On the other hand, the vertical synchronizing signal v obtained from the vertical counter 0 is supplied to the input terminal D of the D flip-flop 12.

The clock terminal CP of this D flip-flop 12 is supplied with a horizontal synchronizing signal h obtained from the output terminal ◯ of the horizontal counter 2. Therefore, even when the horizontal synchronizing signal h rises, the high level of the vertical synchronizing signal v supplied to the input terminal D of the flip-flop 12 is read.
This flip-flop 12 becomes set. The output signal b (FIG. 2b) of the set output terminal Q of this flip-flop 12 is supplied to the input terminal D of the D flip-flop 13. A horizontal synchronizing signal h is supplied to the clock terminal CP of the D flip-flop 13. Therefore, in the same way as the D flip-flop 12, this D flip-flop 13 becomes set at the rising edge of the horizontal synchronizing signal h, and as shown in FIG. A signal c is obtained from the set output terminal Q. Note that the output signal c (FIG. 2c) of the output terminal Q of this D flip-flop 13 and the output signal b of the flip-flop 12 are supplied to a NAND gate 14, respectively.

Therefore, from the output of the NAND gate 14, a switch signal d is formed which is at a low level during the IH period at the rising edge of the vertical synchronizing signal v as shown in FIG. 2d. This switch signal d is supplied to the control terminal S2 of the line selector 7. As a result, the movable contact of the switch 9 of the line selector 7 is connected to the contact 9a only during the high level period of the switch signal d, and the 910 count output of the NAND gate 4 is selected.

Further, when the switch signal d is at a low level during the IH period, the movable support point is connected to the contact point 9b, and the counting output of 91 Kin Hayabusa and 90 Turtle Hayabusa is alternately switched for each IV as described above. I get a signal. As a result, during the first horizontal scanning period of a certain field (field A), the 916 boat counting output a2 of the output of the NAND gate 5 passes through the contact 8a of the switch 8 of the line selector 7 and the contact 9b of the switch 9, and then becomes the output of the horizontal counter 2. It is fed back to the reset terminal R.

Therefore, the horizontal counter 2 is reset after counting 916 ships. After that, the 91G ship count output of NAND Gate 4 a. is fed back to the horizontal counter 2 via the saddle point 9a of the switch 9, so the horizontal counter performs the normal counting operation for 91G ships. Therefore, as shown in FIG. 2e, the synchronizing pulse e obtained from the synchronizing signal forming circuit 3 is during the IH+Q pulse during the first horizontal scanning period 20 of the A field, and thereafter during the normal IH pulse. Also, in the first horizontal scanning period of the next field (B field), the 904 count output a3 of the NAND gate 6 is connected to the contact 8b of the switch 8 of the line selector 7, and the contact 9b of the switch 9.
The signal is fed back to the reset terminal R of the horizontal counter 2 via .

Therefore, the horizontal counter 2 performs a 904-base counting operation and is then reset. Thereafter, the horizontal counter 2 performs the normal counting operation of 91-bok hayabusa in the same manner as described above. Therefore, the synchronization pulse e obtained from the synchronization signal forming circuit 3 is
As shown in FIG. 2e, the first horizontal scanning period 21 of the B field is during the IH-Q pulse, and then the normal I
During H pulse. FIG. 3A shows the horizontal scan lines formed on the television screen by the synchronization pulse e shown in FIG. 2e.

The first scan line 20 of the A field as shown in FIG.
The length of a corresponds to the horizontal scanning period during the IH+Q pulse. The subsequent scanning lines have the length of IH. Therefore, in the A field, the horizontal scanning line is shifted from the horizontal line of the previous field by a distance corresponding to Q. Also, the length of the first scanning line 21a of the B field is
This length corresponds to the horizontal scanning period during the IH-Q pulse.

Therefore, in the B field, the horizontal scanning line is returned by a distance line corresponding to Q. In this way, a synchronizing pulse e that shifts the position of the horizontal scanning line by a predetermined amount every other field.
corresponds to a synchronization pulse obtained when the two magnetic heads of a rotating magnetic head device of a VTR are not mounted on the center line of the head disk at an interval of exactly 180 degrees, but are misaligned. Therefore, such V
An image substantially identical to that formed by TR,
It can be formed by using the synchronization pulse e as a synchronization signal. Note that the above-mentioned amount Q of positional deviation of the horizontal scanning line can be adjusted by variously selecting the counting output of the horizontal counter 2 supplied to the NAND gates 5 and 6. In this way, by looking at the image formed based on the synchronization pulses formed by the circuit shown in Fig. 1, it is possible to quantitatively recognize how the image is affected by the positional deviation of the VTR head. I can do it.

Note that the position of the horizontal scanning line may be displaced a plurality of times (for example, four times) in one field of the screen. In this case, it is possible to reproduce the influence on the screen caused by positional deviation of the magnetic heads of a four-head VTR. Next, a case will be described in which the switch 17 shown in FIG. 1 is closed.

In this case, the switch 26 linked to the switch 17 is closed and the high level power supply voltage of 10 V is applied to the line selector 7.
is supplied to the control terminal S2 of. For this reason, the movable contact of the switch 9 of the line selector 7 is connected to the contact 9a, so the horizontal counter 2 performs a counting operation of 91 ships. In FIG. 1, the mirror-tooth wave forming circuit 16 has a vertical period (IV).
This is a circuit for forming a mirror tooth wave.

That is, the sawtooth wave shown in FIG. 2C is formed based on the vertical synchronization signal V separated from the external video signal. Note that this mirror-tooth wave may also be formed by filling in the vertical synchronizing signal v output from the vertical counter 10. This mirror-toothed wave is supplied to the mixer 15 via an attenuator 23 for adjusting the bell. A further input terminal of the mixer 15 receives the vertical frequency 1/2 v/2 pulse from the flip-flop 11 via an attenuator 23. Further, a signal from an external input terminal 25 is coupled to another input terminal of the mixer 15 via an attenuator 24. mixer 1
The output signal of 5 is applied to the frequency modulation terminal M of the clock pulse generator 1. Therefore, the frequency of the clock pulse generated by the clock pulse generator 1 is modulated depending on the level of the output signal of the mixer 15. attenuator 22,
23 and 24 so that the sawtooth waveform shown in FIG. increases linearly with a vertical period V according to the level of

These clock pulses are counted by a horizontal counter 2 and a vertical counter 10, and various synchronizing signals are formed in a synchronizing signal forming circuit 3 based on the counted outputs. The length of the horizontal scanning line of the television screen formed based on the synchronizing pulse e of the synchronizing signal is periodically shortened with a vertical period V, as shown in FIG. 3B. Distortion occurs in television images formed based on such horizontal scanning lines. The reason why the length of the horizontal scanning line is periodically shortened as described above is because, for example, in a VTR, the axes of the head disk of the rotating magnetic head device and the tape guide cylinder are misaligned with each other, and the magnetic This is a case where the circumferential speed of the head at the tape scanning position differs during one cycle of rotation.

Therefore, an image substantially the same as that formed by such a VTR can be reproduced using the synchronizing pulse e as a synchronizing signal. Next, input a sine wave g of about IH2 (g in Fig. 2) to the external input terminal 25 in Fig. 1, for example.
When this sine wave g is supplied to the frequency modulation terminal M of the clock pulse generator 1 via the attenuator 24, mixer 15, and switch 17, the frequency of the clock pulse changes according to this sine wave g. It fluctuates periodically.

The period of the synchronizing pulse e formed in conjunction with this clock pulse varies, for example, with the IHZ period, and the length of the horizontal scanning line formed based on this synchronizing pulse e also changes periodically. A television image formed using such horizontal scanning lines appears loose in the horizontal direction. Such image fluctuations occur when, for example, there is rotational unevenness in the head disk of a rotating magnetic head device of a VTR.

Therefore, substantially the same image formed by such a VTR can be reproduced by using the synchronizing pulse e as a synchronizing signal. Next v
/2 pulse is passed through the attenuator 23, the mixer 15, and the switch 17 to the frequency modulation terminal M of the clock pulse generator 1.
The clock pulse is frequency modulated according to this v/2 pulse (v/2 in FIG. 2). The synchronizing pulse e formed based on this clock pulse has a short period in the A field section, and a long period in the B field section, for example. The lengths of horizontal scanning lines formed based on this synchronizing pulse e are A field and B field.
Different in the field. In this case, the image formed is shifted left and right for each field, resulting in an unstable image.
The above-mentioned phenomenon occurs when the rotation radius of the A head and the B head differs due to wear of the magnetic head of the rotary magnetic head device of the VTR, and the circumferential speeds of the two heads at the tape scanning position differ.

Therefore, such a phenomenon can be reproduced by using the above-mentioned synchronization pulse e. By adjusting the attenuators 22, 23, and 24, respectively, and mixing the above-mentioned sawtooth wave, sine wave g, and v/2 pulses at various levels in the mixer 15, the above-mentioned various effects can be achieved. It is possible to reproduce VTR images that simultaneously have the following defects. - As described above, the first aspect of the present invention is to change the predetermined number of counting circuits that form an average wave number signal by counting a predetermined number of clock pulses at least once per frame. I made it possible.

The image of any horizontal scanning line of the television image formed based on the synchronization signal obtained from the horizontal frequency signal can be shifted in the horizontal direction. Therefore, VTR, . Easily reproduces television images that are formed when multiple heads of a head device of a video signal recording and reproducing device such as a VSR are not accurately attached to the head mounting body at equal intervals and are misaligned with each other. It is possible to quantitatively recognize the effect that such head positional deviation has on the image. Also the second
The invention uses a counting circuit to count frequency-modulated clock pulses according to a modulation signal of a predetermined shape.
The counting circuit is configured such that a horizontal frequency signal is obtained, and an image of an arbitrary horizontal scanning line of a television image formed by blocking a synchronization signal obtained from this horizontal frequency signal is determined by the predetermined value of the modulation signal. The position is shifted horizontally depending on the shape.

Therefore, if the head mounting body of the head device of a video signal recording/reproducing device such as a VTR or VSR is misaligned with the recording medium support body such as a tape guide cylinder or turntable, the head mounting body If there is rotational unevenness in the relative rotation between the head and the recording medium support, or if the rotation radii of the tips of multiple heads differ from each other, television images formed can be easily reproduced. It is possible to quantitatively recognize the influence on images caused by the above-mentioned defects in video signal recording and reproducing devices such as the above.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment in which the present invention is applied to a synchronizing signal generator for VTR test signals, Fig. 2 is a waveform diagram showing waveforms of each part of Fig. 1, and Figs. 3 A and B are TV FIG. 3 is an explanatory diagram showing horizontal scanning lines formed on a screen. In the symbols used in the drawings, 1 is a clock pulse generator, 2 is a horizontal counter, 3 is a synchronizing signal forming circuit, 10 is a vertical counter, and 20a and 20b are horizontal scanning lines. Figure 1 Figure 3A Figure 3B Figure 2

Claims (1)

Claims: 1. (a) a counting circuit that forms a horizontal frequency signal by counting a predetermined number of clock pulses;
(b) a control circuit for controlling the counting operation of the counting circuit so that the predetermined number can be changed at least once per frame, and a synchronization signal obtained from the horizontal frequency signal; A synchronizing signal generator is capable of horizontally shifting an image of an arbitrary horizontal scanning line of a television image formed based on the above. 2, each comprising: (a) a counting circuit that forms a horizontal frequency signal by counting clock pulses; (b) a clock pulse generator capable of generating frequency-modulated clock pulses in accordance with a modulated signal of a predetermined shape; By counting the clock pulses supplied from the clock pulse generator with the counting circuit, the horizontal frequency signal is obtained from the counting circuit, and based on the synchronization signal obtained from the horizontal frequency signal, A synchronizing signal generator capable of horizontally shifting an image of any horizontal scanning line of a television image to be formed in accordance with the predetermined shape of the modulation signal.